September/2019 FINAL STUDY REPORT Cape May Plant Materials Center Cape May Court House, NJ Revegetative success of native species following chemical and mechanical treatment of invasive European common reed (Phragmites australis ssp. australis) Scott Snell, Natural Resource Specialist ABSTRACT Invasions of nonnative European common reed (Phragmites australis ssp. australis) result in degraded wetland ecosystems that do not provide the same level or variety of ecological functions as healthy wetlands. Areas impacted by common reed invasions are increasing in frequency and area. This study evaluates the use of vegetative treatments to compete and inhibit the invasion of common reed in wetland restoration projects. Common reed was mechanically and chemically controlled in a dominated wetland in Villas, NJ. Five native species [crimson eyed rosemallow (Hibiscus moscheutos), High Tide Germplasm switchgrass (Panicum virgatum), Southampton Germplasm prairie cordgrass (Spartina pectinata), sugarcane plumegrass (Saccharum giganteum), and eastern gamagrass (Tripsacum dactyloides)] were planted in replicated single species plots following control measures. The degree of success of the native species was assessed by examining survival, percent coverage, and common reed biomass production after one and two growing seasons. The percent cover of common reed was significantly lower in High Tide Germplasm switchgrass and Southampton Germplasm prairie cordgrass plots than control plots both years. The amount of common reed biomass production was significantly lower in the High Tide Germplasm switchgrass plots than the control plots after one growing season. Crimson eyed rosemallow had the greatest survival rate. High Tide Germplasm switchgrass and Southampton Germplasm prairie cordgrass survival were average (both > 50%). While sugarcane plumegrass and eastern gamagrass both had 0% survival after the second growing season. Results suggested that certain native plant species are more apt to coexist in areas impacted by common reed invasions. Additionally, the findings show that appropriate vegetative practices may slow the spread or reinvasion of treated areas; however, they are unlikely to completely prevent either. INTRODUCTION The importance of wetland ecosystems and the value of the functions they perform has been extensively documented. However, many of the benefits of wetlands are negatively impacted when these ecosystems become degraded due to invasive plant invasions (Hazelton et al., 2014). One of the most common and aggressive exotic plant invaders of wetlands is nonnative European common reed (Phragmites australis ssp. australis). Common reed affected areas appear to be increasing in frequency and expanding in area (Ailstock et al., 2001). Studies have linked common reed invasions with reduced plant diversity, degradation of fish and wildlife habitat, and disturbances to biogeochemical cycles (Chambers et al., 1999; Fell et al., 2003; Meyerson et al., 1999). Successful control of common reed is the first step in restoring these degraded wetlands, Snell, Natural Resources Specialist, 1536 Route 9 Cape May Court House, NJ, 609-465-6354 but control of common reed does not necessarily lead to successful volunteer establishment of the native plant community. Active native plant establishment following invasive plant control can assist the process of building the native plant community as well as slow or prevent reinvasion (Burdick, 2006; Fargione and Tilman, 2005). Determining alternative native plants to compete with and control the spread of common reed was identified as a need in the 2014 and 2015 Northeast Region Plant Materials needs assessment survey. A literature review revealed extensive research on common reed control methods and their varying degrees of success. However, there is a lack of research focusing on revegetation success following invasive species control with only one-third of studies reviewed evaluating revegetation success (Kettenring and Adams, 2011). This study examines the use for revegetation of five native species: crimson eyed rosemallow (Hibiscus moscheutos), High Tide Germplasm switchgrass (Panicum virgatum), Southampton Germplasm prairie cordgrass (Spartina pectinata), sugarcane plumegrass (Saccharum giganteum), and eastern gamagrass (Tripsacum dactyloides). Crimson eyed rosemallow is a native obligate wetland plant common to brackish and freshwater marshes, swamps, floodplains, and alluvial meadows (Reeves, 2008). The typical environment in which crimson eyed rosemallow thrives is like that of common reed. In the Maryland region of the Chesapeake Bay, they have been reported to frequently occur as codominant species (Sipple, 1978). Hoy and Burdick (2005) reported that crimson eyed rosemallow was surviving at several brackish marsh sites in New Hampshire invaded by common reed. Under ideal conditions, crimson eyed rosemallow can form nearly monospecific stands as the sole dominant plant species which may make it an ideal species to compete against common reed (Cahoon and Stevenson, 1986). Switchgrass is a native, warm season, perennial grass assigned a wetland indicator status of facultative for the Northcentral and Northeast region; it is equally likely to occur in wetland and non-wetlands within the region (Lichvar, 2014). High Tide Germplasm switchgrass is a tested plant released by the Cape May Plant Materials Center, Cape May, NJ in 2007. High Tide Germplasm switchgrass originates from a collection site near Perryville, MD at the intertidal zone where the Susquehanna River meets the Chesapeake Bay. High Tide Germplasm switchgrass is particularly valuable for stabilizing tidal shorelines and streambanks (USDA- NRCS, 2012). Given its collection location and use in similar environments, it was identified as having a high likelihood to survive and impede the spread of common reed. In a study examining and testing anecdotal accounts of common reed control measures used by salt-hay (saltmeadow cordgrass [Spartina patens]) farmers in New Jersey, Bart (2010) reported an account of one farmer that mowed a common reed dominated plot biweekly as a means of control. The common reed was eradicated after one growing season and the plot was repopulated by volunteer switchgrass. Prairie cordgrass is a native, perennial grass with a facultative wetland indicator status for the Northcentral and Northeast region meaning that it most commonly occurs in wetlands, but may occur in non-wetlands within the region (Lichvar, 2014). Southampton Germplasm prairie cordgrass is a selected class conservation plant released by the Cape May Plant Materials Center, Cape May, NJ in 2013. Southampton Germplasm prairie cordgrass was selected for erosion control applications on streambanks, spillways, and drainage channels (USDA-NRCS, 2013). 2 Southampton Germplasm prairie cordgrass has displayed some success in impeding the reinvasion of some exotic, invasive species. In a trial from 2007 to 2010 in Lamb’s Creek (Mansfield, PA), Southampton Germplasm prairie cordgrass was shown to successfully compete with and minimize the spread of Japanese knotweed (Polygonum cuspidatum) following two years of chemical and mechanical treatments (Van der Grinten et al., 2011). Hoy and Burdick (2005) reported that stands of prairie cordgrass coexist at a brackish marsh site in New Hampshire that had been invaded by common reed. Sugarcane plumegrass is a perennial, facultative wetland grass for all regions (Lichvar, 2014). Forming clumps, it grows best at the edges of ponds and streams, in bogs and saturated ditches, and tidal freshwater marshes (NPIN, 2011). Because it has been documented to spread readily by seed and shares many of the same ideal environmental characteristics with common reed, sugarcane plumegrass was included in this study (Mellichamp, 2014). Eastern gamagrass is a native, warm season, perennial grass assigned a wetland indicator status of facultative for the Northcentral and Northeast region (Lichvar, 2014). Research has shown that eastern gamagrass regularly forms aerenchyma regardless of soil conditions. The research suggests that the formation of aerenchymous roots may allow eastern gamagrass roots to persist in anaerobic, water logged soils (Clark et al., 1998). This could explain why the native habitat of eastern gamagrass includes swales, salt marsh borders, stream banks, lowlands, and other saturated conditions (NPIN, 2006; Stubbendieck et al., 1992). Given the research findings and the extent of its native habitat conditions, eastern gamagrass was thought to have potential to survive in similar conditions as common reed. The objective of this study is to evaluate the success of these native species to compete with and inhibit the reinvasion of common reed in wetland restoration projects. The findings of this study could be of value to conservation planners addressing degraded plant condition resource concerns with inadequate structure and composition or excessive plant pest pressure in a wetland environment. These findings could be applicable to conservation practices Wetland Wildlife Habitat Management (644), Wetland Restoration (657), Wetland Creation (658), and Wetland Enhancement (659). MATERIALS AND METHODS This study was conducted in an area of a tidally influenced, fresh water high marsh ecosystem at the north end of Villas, NJ (39.038023, -74.929142). The soil type of the entire study area is a Mispillion-Transquaking-Appoquinimink complex (MmtAv). The common reed infestation of the study area formed a dense monoculture